Results
Light microscope (LM) and scanning electron microscope (SEM)
measurements
Sizes of pollen grains were calibrated by lengths of equatorial axis and
polar axis under light microscopy. The average length of grain samples
is 27.31 μm in Polar view (14.4- 51.7μm) and 30.62 μm on polar axis in
equatorial view (18.33- 60.7 μm) (Table 3; Figure 2 and 3). Pollen
shapes were classified as categories by Erdtman (1952). Under light
microscope measurements, the shape of pollen grains ranges from
suboblate (P/E = 0.75-0.88), through oblate-spheroidal,
prolate-spheroidal, and subprolate, to prolate (P/E = 1.33-2). The range
of P/E index of all specimens is from 0.75 to 1.84. There is significant
difference in P/E ratios between three Quercus sections and
between 22 oak species. Polar area (p/D ) is the ratio of the
distance between two furrows and the length of the grain in polar view.p /D of all specimens is from 0.21 to 1.17 (average in 0.64)
(Table 3; Figure 4, 5, and 6). I applied T-test on 20 species
(excluding hybrid Quercus , Chrysolepis , andNotholithocarpus ). The results suggest that there are significant
different between sizes and shapes of each species, each section, and
evergreen-decidous oaks (Table 4). Then, I applied Moran’s tests on 20
species (excluded hybrid species, Chrysolepis chrysophylla , and Notholithocarpus densiflorus ) to test phylogenetic signals. There
is only the length of polar view passed Moran’s test
(p <0.05; p = 0.041 and 0.042 in 2 tests) when I tested 20 species at the same time (Table 5 and 6).
Most California Quercus pollen have scabrate or verrucate
ornamentations on surface. The surface structural patterns of exine
displayed under SEM are psilate-verrucate, verrucate,
verrucate-scabrate, and psilate-scabrate (Table 7). Structural patterns
include perforations of varying density (sparse or dense) and varying
distribution (regular or irregular). Most modern Quercus species
irregularly perform scabrates on pollen surface.